The present invention relates to producing gallium nitride (GaN) by the metathesis of Li3N and a trivalent gallium compound such as GaCl3, GaBr3, or GaI3. Because this reaction is highly exothermic, decomposition of the product into elemental Ga and N2 normally occurs, thereby reducing yields.
To deal with this problem, it has already been proposed to carry out the reaction in the presence of high pressure nitrogen. For example, Kaner and coworkers found that, by applying high pressure (4.5 GPa), they could suppress evolution of N2 gas from the reaction of GaI3 and Li3N and produce GaN in 87% yields. See, Wallace et al., Appl. Phys. Lett. 1998, 72, 596. However, high pressures limit the scale of the reaction to producing minute quantities of product as a practical matter.
Another approach for controlling decomposition in this reaction has been to add a substance that acts as a heat sink. For example in a subsequent study, Kaner and coworkers performed this reaction in the presence of NH4Cl and/or LiNH2 additives. See, Wallace et al., Chem. Mater. 1999, 11, 2299; and Cumberland et al., J. Phys. Chem. B 2001, 105, 11922. Similarly, Xie and coworkers studied the reaction of GaCl3 with Li3N in an organic solvent such as benzene near its critical point. See, Xie et al., Appl. Phys. Lett. 1996, 69, 334; and Xie et al., Science 1996, 272, 1926. After 6-12 hours, dark gray, nanocrystalline GaN powder was recovered. While these approaches limited decomposition of the GaN product, they also significantly reduced reaction rates and yields to unacceptably low levels.
In still another approach, Wells and Janik studied the reaction between GaBr3 and Li3N in refluxing diglyme and xylene. See, Wells et al., Eur. J. Solid. State Inorg. Chem. 1996, 33, 1079. However, product yields obtained after 80 hours were low and, moreover, the powdered product obtained was highly contaminated with elemental gallium.